The present invention relates to packaging for products, such as food products, that are initially enclosed under certain environmental conditions in a gas-impermeable, heat-shrunk bag. The bag includes an outer, gas-impermeable portion that peelably delaminates (i.e., delaminates upon peeling) to expose an inner, gas-permeable portion, thereby causing a change in the environmental conditions within the package. More specifically, the invention relates to such packaging for fresh red meat and poultry products.
Historically, large sub-primal cuts of meat have been butchered and packaged in each supermarket. This arrangement has long been recognized to be inefficient and expensive. It would instead be preferable to butcher and package the meat at a central processing facility which benefits from economies of scale, and then ship the packaged meat to individual supermarkets or other retail outlets such as is done, for example, with many poultry products. It is believed that central processing of meat would also lead to a higher quality, more sanitary product with a longer shelf-life than meat which is butchered and packaged in individual supermarkets.
Fresh red meat presents a particular challenge to the concept of centralized processing and packaging due to its oxygen-sensitivity. Such oxygen-sensitivity is manifested in the shelf-life and appearance (color) of a packaged meat product. For example, while a low-oxygen packaging environment generally increases the shelf-life of a packaged meat product (relative to meat products packaged in an environment having a higher oxygen content), red meat has a tendency to assume a purple color when packaged in the absence of oxygen or in an environment having a very low oxygen concentration, i.e., below about 5% oxygen. Unfortunately, such a purple color is undesirable to most consumers, and marketing efforts to teach the consumer about the acceptability of the purple color have been largely ineffective. When meat is exposed to a sufficiently high concentration of oxygen, e.g., as found in air, it "re-blooms" to a bright red color which most consumers associate with freshness. After 1 to 3 days of such exposure, however, meat assumes a brown color which, like the purple color, is undesirable to most consumers (and indicates that the meat is beginning to spoil).
Thus, in order to effectively butcher and package meat products in a central facility for distribution to retail outlets, the meat would desirably be packaged, shipped, and stored in a low-oxygen environment for extended shelf-life, and then displayed for consumer sale in a relatively high-oxygen environment such that the meat is caused to re-bloom to a red color just before being placed in a retail display case. While in the retail display case, the meat product is desirably contained in a package which protects it from microbial and other contamination. In order to attain the maximum economic benefit from centralized packaging, the package in which the meat product is displayed for consumer sale is the same package in which the meat product is initially packaged and shipped from the central processing facility. As can be appreciated, centralized butchering and packaging of fresh red meat presents a number of difficult packaging challenges.
A variety of packages have been developed in an effort to overcome the foregoing challenges. One class of such packages is known as "vacuum skin packaging," in which a product to be packaged has traditionally been placed on a supporting member, such as a rigid or semi-rigid tray, and essentially serves as a mold for a thermoformable film which is formed about the product and adhered to the tray by means of heat and differential air pressure. Virtually all of the air is evacuated from the interior of the package so that the film conforms very closely to the contour of the packaged product (see, e.g., U.S. Pat. Nos. Re. 30,009 (Purdue et al.) and 5,346,735 (Logan et al.), the disclosures of which are hereby incorporated herein by reference). When used to package fresh red meat products, it is necessary for both the film formed around the product and the support member to present a barrier to the passage of gases therethrough, particularly oxygen such as is found in air, which are detrimental to the shelf or storage life of fresh red meat. The thermoformed film generally includes both a gas-permeable film in contact with the product and a substantially gas-impermeable film which is peelably adhered to the gas-permeable film so that the gas-impermeable film may be peelably removed from the gas-permeable film, thereby allowing the meat product to re-bloom to the customer-preferred red color, e.g., at retail, while still being protected from dust, dirt, and other contaminates by the remaining gas-permeable film.
While traditional vacuum skin packaging as described above has proven to be advantageous for many packaging applications, difficulties in peeling the gas-impermeable film from the gas-permeable film can occur when the packaged meat product has a relatively high profile or is relatively bulky, such as, e.g., fresh beef roasts, in comparison with smaller cuts of meat such as steaks. For such high-profile meat cuts, a different type of "re-bloomable" package has been developed in which the meat product is first placed into a gas-permeable pouch and then the interior of the pouch is evacuated and the pouch is sealed closed. The sealed gas-permeable pouch with the meat product therein is next placed into an outer, gas-impermeable pouch, and a second vacuum and sealing step is performed to enclose the gas-permeable pouch within the gas-impermeable pouch. When it is desired to display the meat product for customer purchase at retail, the outer pouch is opened and the inner, gas-permeable pouch is placed in a display case after the meat product has re-bloomed (by virtue of oxygen contact with the meat via the gas-permeable inner pouch). While such a package avoids the peeling difficulties attendant with vacuum-skin packaging of high-profile meat cuts, other problems are encountered. It is desired for the inner pouch to be tightly contoured to the surface of the meat product. This is both for aesthetic reasons and to minimize purge, i.e., unsightly juices from the meat which otherwise collect between the meat surface and interior surface of the inner pouch. It has been found, however, that the second vacuum step causes the inner pouch to assume a looser fit about the meat product, thereby allowing purge to accumulate between the meat product and pouch. Not only is such a condition commercially unacceptable from an aesthetic standpoint, but the amount of time that the meat product stayed in bloom was found to decrease from the normal three-day period to approximately one day. Moreover, from a packaging standpoint, the two-step vacuum and sealing operation is an unacceptably long and cumbersome process.
Accordingly, there is a need in the art for a re-bloomable package for high-profile meat products which avoids the foregoing shortcomings of coventional packages.